Stabilized iron pentacarbonyl and motor fuel containing the same



Patented Jon. 3, 1950 STABILIZED IRON PENIACARBONYL AND MOTOR FUEL CONTAINING ,THE SAME Robert Edward Christ, Elizabeth, N. 1., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application May 21, 1946, Serial No. 671,401

(Cl. 4H7

Claims.

This invention relates to liquid fuels suitable for use in internal combustion engines. More particularly, it relates to .the use of iron pentacarbonyl as an anti-knock agent in motor fuels and to iron pentacarbonyl of improved stability to light and air.

It is known that iron pentacarbonyl possesses-- the property of raising the octane value of gasoline. It is ideal in many respects as an antiknock, a very small amount, less than 0.1% by volume, being sufllcient to raise the octane rating of gasoline to a high value It is very soluble in gasoline, substantially inert with respect to the parts of the enginewith which it comes in contact, and in concentrated or diluted form does not cause poisoning on contact with the skin.

Despite its many advantages, iron pentacarbonyl, Fe(CO) s, has not attained commercial success as an anti-knock agent due to its inherent instability to light by which it is rapidly decomposed, this decomposition being most rapid in sunlight or blue light and least so in red light. The decomposition is a progressive change, the first product being iron enneacarbonyl, Fe2(CO) 9, which comes down in the form of glistening golden-yellow plates according to the following reaction,

followed by a further decomposition with production of a voluminous black precipitate of ferrous oxide and other iron compounds.

This decomposition not only results in loss of octane value from the initially high level obtained in the gasoline with the freshly dissolved iron pentacarbonyl but also renders the gasoline unfit as a motor fuel due to the propensity of the precipitate to clog the gasoline line or the carburetor.

I have now found that motor fuels of high quality, which in the presence of sunlight and air exhibit a high degree of permanency in respect to anti-knock characteristics and freedom, from formation of precipitates derived from the anti-knock agent, may be obtained from gasoline of low octane value and iron pentacarbonyl by employing in conjunction with the latter certain compounds, hereinafter more particularly defined, which act as stabilizers for the iron pentacarbonyl. v

The present invention resides in my discovery that iron pentacarbonyl may be rendered substantially permanently resistant to decomposition by'light and air when there is intimately associated therewith a hydrocarbon-soluble allphatlc hydroxy polycarboxylic acid partial aliphatic ester-aliphatic amide. These compounds are acid-reacting by virtue of the free carboxyl group or groups.

The term partial as usual herein, is employed in the usual sense to define ester-amides in which part of the carboxyl groups of the hydroxy polycarboxyl-ic portion of the ester-amide molecule are esterfled and part amidifled, but one or more are free.

For improving the stability of iron pentacarbonyl to light and air, the partial ester-amides may be employed in widely varying amounts, ranging from about 1% to about 50% by volume on the iron pentacarbonyl. The amount necessary in each instance to render the iron pentacarbonyl substantially permanently stable to light and air may vary with the individual acid-reacting ester-amides, but, in general, it will be about 5 to 10% by volume on the iron pentacarbonyl.

In the practice of the invention for the preparation of motor fuels of increased anti-knock characteristics the iron pentacarbonyl, which is a liquid, and the stabilizer are simply dissolved in the gasoline or other liquid base fuel to be treated, the mixture being stirred to insure uniformity in dispersion of the iron pentacarbonyl and the stabilizer therein. The iron pentacarbonyl, it-- self, is employed in amounts of 1 to 4 cc. or more per gallon of the liquid motor fuel, a preferred proportion based on a gasoline of -65 octane number being from 3 to 4 cc. per gallon of the gasoline. It will be understood, of course, that the proportion of iron pentacarbonyl used will depend on the initial octane value of the liquid fuelto be treated and as well on the level to which this value is to be lifted by the treatment. Generally, the lower the octane rating of the liquid fuel, the greater should be the proportion of iron pentacarbonyl added thereto.

The iron pentacarbonyl and stabilizer may be added separately to the liquid fuel, or, as is preferred, they are added together from a concentrate which isa blend of the iron pentacarbonyl, the stabilizer, and a small proportion of a mutual organic solvent therefor which is compatible as an ingredient of the liquid motor fuel, suitably, a portion of the liquid fuel of the kind to be treated. "The stabilized concentrate may be stored over long periods of time without lossin iron pentacarbonyl through decomposition.

Concentrates of stabilized iron pentacarbonyl may be conveniently, and are preferably, prepared by first dissolving the partial ester-amide in a relatively small quantity of gasoline, kerosene. benzol or other solvent compatible with the motor fuel and then adding the iron pentacarbonyl to this solution with stirring to effect a homogeneous mixture. A suitable proportion of solvent and iron pentacarbonyl in the concentrates is about equal volumes of the two, although this proportion may be varied somewhat where particular concentrations of iron pentacarbonyl are desired.

The motor fuels which may be treated with the stabilized anti-knock agent for improvement in octane value may be any of'the usual liquid hydrocarbon fuels such as kerosene, gasolines, straight-run, cracked or so-called "poly gasoline, or blends of these with benzol, alcohol or the like, Diesel fuels of the Fischer-Tropsch type, or other types, such as alcohols, in which the iron pentacarbonyl and stabilizer are soluble.

By the term hydrocarbon-soluble as used herein is meant that the substance so-designated is soluble in kerosene, gasoline, benzol and the like liquid hydrocarbons.

As a specific example of stabilized anti-knock concentrates which may be prepared in accordance with the invention is the following composition in which was blended in the preferred manner, by volume,

Parts Partial ester-amide of citric acid from octadecyl alcohol and octadecylamine 2 Gasoline 22 Iron pentacarbonyl 20 When mixed with a gasoline of octane number 65 in the proportion of 8.8 cc. to the gallon of gasoline, the mixture represents a motor fuel of 75 octane number which retains its high antiknock quality over long periods of time on exposure to air or sunlight.

Further illustrative of the compounds which may be employed in accordance with the invention for improving the stability of iron pentacarbonyl to light and air, are, for example, the

'h'ydrocarbon-soluble partial aliphatic ester-aliphatic amides of saturated. aliphatic hydroxy polycarboxylic acids having three or more carboxyl groups, such as citric acid, isocitric acid, hydroxy citric acid, I-hydroxy-l-carboxysuccinic acid, 1-hydroxybutane-1,2,3-tricarboxylic acid, l-hydroxybutane-1,2,4-tricarboxylic acid, 3-hydroxybutane-1,1,5-tricarboxylic acid, 2-hydroxy-4-methylpentane-1,1,2,4 tetracarboxylic acid and 1,6-dihydroxyhexane-2,2,5,5-tetracarboxylic acid, where the ester group or groups are derived from an aliphatic m'onohydric alcohol in which the alkyl radical thereof contains four or more carbon atoms and is unsubstituted or contains substituents not giving rise to corrosive fumes in the engine on cumbustion of the motor fuel containing the same, such as chlorine or bromine atoms, for example, n-butyl alcohol, ter iary butyl alcohol, 4-chloro-n-butyl alcohol, 1-biomo-2-hydroxybutane, 2-ethyl butanol, methyl amyl alcohol, hexanol, heptanol-2, octanol-l, 2-ethylhexanol, undecanol, dodecanol, tetradecanol, heptadecanol, octadecanol, oleyl alcohol, cyclohexyl alcohol, etc., and the amide .group or groups from an aliphatic amine, the ,alkyl radical of which contains four or more carbon atoms and which is unsubstituted or contains substituents, such as chlorine or bromine atoms or alkoxy groups, for example, n-dibutylamine, 2-ethylhexylamine,di-2-ethy1-hexylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, cyclohexylamine,

p-chlorobutylamine, p-bromobutylamine. p-ethoxybutylamine, etc.

Preferably, the ester and amide groups of the esteramldes contain the longer chain hydrocarbon radicals, for example, of about 8 or more carbon atoms in the case of the ester groups and of about 10 or more carbon atoms in the case of the amide groups, as the longer the hydrocarbon chain thereof, generally the greater the hydrocarbon solubility of the ester-amide molecule.

The saturated aliphatic hydroxy polycarboxylic acid partial aliphatic ester-aliphatic amides may be prepared in any manner found suitable. Following known procedure (Karrer, Organic Chemistry, New York, 1938, page 199) they may be prepared irom the corresponding acid esters of the saturated aliphatic hydroxy polycarboxylic acids by heating the acid ester with a solution of the amine taken in "quantity suflicient to replace part only of the ester groups. For example, citric acid partial oleyl esteroleyl amide may be prepared by heating one mol of citric acid dioleyl ester with a solution of one mol of oleyl amine. The acid esters of the hydroxy polycarboxylic acids may be prepared in known way for the esterification of carboxylic acids. Obviously, the temperature to which the reactants are heated.

should be below that at which dehydration of the hydroxy carboxylic compound occurs through loss therefrom of the alcoholic hydroxy group. A

' preferred hydroxy polycarboxylic acid for the contains at least four carbon atoms, the amount preparation of the ester-amides is citric, preferred, however, only from the standpoint of ready availability from natural sources. Other preferred hydroxy polycarboxylic acids are those containing a plurality of hydroxy groups, such as hydroxy citric acid.

In addition to their action as stabilizers for the iron pentacarbonyl in the motor fuel, the herein-defined partial aliphatic ester-aliphatic amides favorably influence the removal of the residue of the iron pentacarbonyl from the internal combustion engine. In this respect it has been observed that the residue is almost completely removed from the combustion areas of the engine and emerges from the exhaust as a light, flufiy red powder.

As various other embodiments of the invention will occur to those skilled in the art, it is not intended that the scope of the patent be limited except as is required by the prior art and the appended claims.

I claim:

1. A composition comprising iron pentacarbonyl blended with a minor proportion of a hydrocarbon soluble partial alkyl ester-alkyl amide of a saturated aliphatic hydroxy polycarboxylic acid of at least three carboxyl groups, in which the hydroxy portion is free and the alkyl radical of the ester and amide groups in each instance of the alkyl ester-alkyl amide being sufficient to increase the stability to light of the iron pentacarbonyl.

2. A composition comprising iron pentacarbonyl blended with a minor proportion of a hydrocarbon soluble partial alkyl ester-alkyl amide of citric acid in which the hydroxy portion is free and the alkyl radical of the ester and amide groups in each instance contains at least four carbon atoms. the amount of the alkyl esteralkyl amide being suflicient to increase the stability to light of the iron pentacarbonyl.

3. A composition comprising iron pentacar bonyl blended with a minor proportion of citric acid partial stearyl ester-stearyl amide, the amount or the latter being sufllcient to increase the stability to light of the iron pentacarbonyl.

4. A motor fuel comprising'a liquid base fuel and dissolved therein a minor proportion 01' iron pentacarbonyl and of a hydrocarbon-soluble partial alkyl ester-alkyl amide of a saturated aliphatic hydroxy polycarboxylic acid of at least 3 carboxyl groups, in which the hydroxy portion is free and the alkyl radical of the ester and amide groups in each instance contains at least four carbon atoms, the amount of the alkyl esteralkyl amide being suflicient to increase the stability to light of the iron pentacarbonyl.

5. A motor fuel comprising a liquid hydrocarbon iuel and dissolved therein a minor proportion of iron pentacarbonyl and of a hydrocarbon-soluble partial alkyl ester-alkyl amide of a saturated aliphatic hydroxy polycarboxylic acid of at least 3 carboxyl groups, in which the hydroxy portion is free and the alkyl radical of the ester and amide groups in each instance contains at least four carbon atoms, the amount of the alkyl ester-alkyl amide being sufllcient to ingrease the stability to light of the iron pentacaronyl.

6. A motor i'uel comprising a liquid hydrocarbon fuel and dissolved therein a minor proportion of iron pentacarbonyl and of a hydrocarbon-soluble partial alkyl ester-alkyl amide of citric acid in which the hydroxy portion is free and the alkyl radical or the ester and amide groups in each instance contains at least four carbon atoms, the amount of the alkyl ester-alkyl amide being sufflcient to increase the stability to light 01 the iron pentacarbonyl.

7. A motor i'uel comprising a liquid hydrocarbon fuel and dissolved therein a minor proportion of iron pentacarbonyl and of citric acid partial stearyl ester-stearyl amide, the amount of the latter being sumcient to increase the stability to light of the iron pentacarbonyl.

8. 'A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about 1 to about by volume on the pentacarbonyl of a hydrocarbon-soluble partial alkylesteralkylamide of a saturated aliphatic hydroxy polycarboxylic acid of at least 3 carboxyl groups, in which the hydroxy portion is free and the alkyl radical of the ester and amide groups in each instance contains at least 4 carbon atoms, and an amount of a liquid hydrocarbon solvent sufficient to dissolve the pentacarbonyl and the partial alkylester-alkylamide.

9. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, from about 1 to about 50% by volume on the pentacarbonyl of a hydrocarbon-soluble partial alkylester-alkylamide of citric acid, in which the hydroxy portion is free and the alkyl radical of the ester and amide groups in each instance contains at least 4 carbon atoms, and an amount of a liquid hydrocarbon solvent suflicient to dissolve the pentacarbonyl and the partial alkylesteralkylamide.

10. A stabilized iron pentacarbonyl concentrate consisting essentially of iron pentacarbonyl, ,from about 1 to about 50% by volume on the pentacarbonyl of citric acid partial stearyl ester-stearyl amide, and an amount of a liquid hydrocarbon solvent suflicient to dissolve the pentacarbonyl and the citric acid partial stearyi ester-stearyl amide.

ROBERT EDWARD CHRIST.

No references cited. 

1. A COMPOSITION COMPRISING IRON PENTACARBONYL BLENDED WITH A MINOR PROPORTION OF A HYDROCARBON SOLUBLE PARTIAL ALKYL ESTER-ALKYL AMIDE OF A SATURATED ALIPHATIC HYDROXY POLYCARBOXYLIC ACID OF AT LEAST THREE CARBOXYL GROUPS, IN WHICH THE HYDROXY PORTION IS FREE AND THE ALKYL RADICAL OF THE ESTER AND AMIDE GROUPS IN EACH INSTANCE CONTAINS AT LEAST FOUR CARBON ATOMS, THE AMOUNT OF THE ALKYL ESTER-ALKYL AMIDE BEING SUFFICIENT TO INCREASE THE STABILITY TO LIGHT OF THE IRON PENTACARBONYL. 